Sodium block and depolarization diminish P2Z-dependent Ca2+ entry in human B lymphocytes

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Item Type:	Article
Title:	Sodium block and depolarization diminish P2Z-dependent Ca2+ entry in human B lymphocytes
Creators Name:	Loehn, M., Klapperstueck, M., Riemann, D. and Markwardt, F.
Abstract:	Despite a high Ca2+-permeability of the P2Z receptor in human B lymphocytes, extracellular ATP4- has only a minor effect on global [Ca2+]i. The aim of this study was to reveal the mechanisms responsible for this discrepancy. We investigated the relationship between ATP4-application, Cai 2+-response, membrane current and membrane potential in two human B cell lines and in human tonsillar B cells. This was achieved by a combination of FACS- and voltage clamp measurements and the usage of appropriate voltage- and Ca2+-sensitive fluorescent dyes. ATP4-induced changes in whole-cell current and [Ca2+]i were blocked by extracellular as well as intracellular Na+. Under current clamp conditions, ATP4--induced Na+-entry diminished the Ca2+ entry via reduction of the driving force. A substantial increase in [Ca2+-]i induced by ATP4- was only observed in Na+-free solutions. The pathway of signal transduction activated by ATP4- via P2Z receptor of human B lymphocytes under physiological conditions seems not to operate by an increase in the global intracellular Ca2+-concentration, but rather by the depolarization of the cell membrane as a result of the Na+-influx.
Keywords:	Adenosine Triphosphate, B-Lymphocytes, Calcium, Cell Membrane, Cultured Cells, Extracellular Space, Flow Cytometry, Membrane Potentials, Purinergic P2 Receptors, Signal Transduction, Sodium, Tonsil
Source:	Cell Calcium
ISSN:	0143-4160
Publisher:	Elsevier
Volume:	29
Number:	6
Page Range:	395-408
Date:	1 January 2001
PubMed:	View item in PubMed

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